In an elevator system, the operation of the elevators is controlled on the basis of calls entered by users. In a conventional elevator system, call input is in most cases arranged by placing on each floor of the building up/down buttons, by means of which an arriving passenger indicates the desired traveling direction. In addition, the elevator car needs to be provided with a control panel, on which the elevator passenger presses the button corresponding to his/her desired destination floor. In the traditional call input method, the elevator customer thus inputs two calls. First, a call button has to be pressed to call an elevator to the floor where the customer is currently located. In addition to this, a second press of a call button is needed in the elevator car.
An indicator light, which may have the shape of e.g. a direction arrow, is generally placed near the landing call buttons, i.e. near the up/down buttons outside the elevator car. A signal light lit in such a direction arrow indicates the traveling direction of an elevator having arrived at the floor. In addition, the landing may be provided with a digital number display placed beside or above the elevator door and continuously showing the floor at which the elevator is currently located.
FIG. 1 presents the parts of a traditional elevator system, wherein an elevator group 111 in the elevator system comprises one or more elevator cars 11, an elevator control panel 12, an elevator group control system 13 and an elevator control system 14.
The elevator group control system 13 receives the landing call entered via the up/down buttons and tries to determine which one of the elevators in the elevator group will be best able to serve the person having entered the call. The landing call comprises information indicating the user's starting floor and whether the user is traveling in the upward or downward direction. The process of determining which elevator will be suitable for the user is termed call allocation. In continuous allocation, the control system 13 keeps continuously selecting, e.g. at half-second intervals, a suitable elevator for the user. Often a landing call is allocated to the elevator that is located closest to the user and traveling in the direction of the call. In continuous allocation, the actual selection of an elevator is not made until the elevator is so close to the floor of the call that it must begin to decelerate in order to stop. At this stage, the group control system 13 allocates the landing call to the stopping elevator car and transmits the received landing call to the elevator control system 14. Once the control system 13 has determined which elevator is to serve the user, the user can give his/her destination floor by pressing the desired button in the control panel 12. One of the advantages of continuous allocation is that, if an elevator traveling towards the user's starting floor stops before reaching the user's floor and remains stationary for some time, there may arrive from elsewhere another elevator that reaches the user's floor much earlier than that elevator car which seemed best at the time of entry of the landing call.
FIG. 2 presents an elevator system employing another call method. In the destination-floor elevator system according to FIG. 2, the user selects his/her destination floor already in the elevator lobby outside the elevator 21. In destination-floor elevator systems, each user wanting to have a ride on an elevator enters at the landing a destination floor call, which comprises information indicating the user's starting floor, destination floor and possibly some other information, such as the number of passengers or the like. In destination-floor elevator systems, the number of calls to be entered per elevator ride is one instead of the traditional two calls.
A destination floor call is entered e.g. using a destination call device 25 specifically reserved for this purpose, which is an expanded version of the traditional landing call button and is mounted at the landing. In the destination call device, the traditional landing call button has been expanded with a more versatile user interface so as to allow the user to directly indicate the floor he/she wants to reach by elevator. The destination floor call is transmitted for elevator allocation to the group control system, i.e. to the elevator control system 24, which immediately allocates an elevator to serve the user, specifically for each case e.g. on the basis of a genetic algorithm, and sends to the destination call device information regarding the elevator reserved for the user. Elevator allocation performed immediately is called single allocation. In this case, allocation takes place at the moment when the control system 24 receives a destination floor call from a user and the allocation is not changed afterwards. A simplified control panel 22 placed in the elevator car comprises e.g. a digital number display showing the floors at which the elevator is going to stop.
In traditional landing call allocation, it is difficult to utilize the entire transport capacity of the elevator group as well as simultaneous calls of a plurality of users. Neither is it possible in the traditional control method to optimize the total travel time of each passenger on a passenger-specific basis. By contrast, a destination-floor elevator system takes each passenger's total travel time and the number of users into account and can thus serve the users of the system more effectively. In a destination-floor elevator system, it is also possible to gather users with the same destination floor in the same elevator, thus allowing fast and efficient operation of the elevator system. However, the elevator control needed in a destination-floor elevator system requires for group control a very complex control system, which is not necessary in smaller elevator systems. The control tables required in a destination-floor elevator system also require plenty of memory storage space and are additionally impractical in respect of price in the case of smaller elevator systems.
Moreover, a destination-floor elevator system requires complicated signaling, such as displays mounted at the landings to let the user know in which direction the elevator selected to serve the call is moving and at which floors it will stop.